Rokinon 14mm for Canon with focus chip

I have been looking for a UWA for my Canon full-frame and thought about buying the Rokinon lens as an inexpensive alternative to the Canon UWA. The Rokinon is a manual focus lens but I saw on one of the Amazon reviews of this lens that the purchaser also bought a "focus chip" on eBay for use with his Canon camera and this lens. Given that I was wondering -

1) What is a focus chip?

2) Does something like that really work with a manual focus lens? and

3) How hard is manual focus with a lens like this considering that the new cameras are really designed for auto focus and no longer have the old fashioned focus screens which would allow accurate manual focus.

Thanks for any help.